off-the-record
dark
crypto-
mum
occulted
under wraps
subterranean
secretomal
closehanded
secernent
on the down-low
under the covers
closehandedness
pseudosecret
clandescent
concealment
underhand
ultrasecret
top secret
secretomics
exposure
backstage
keep a lid on
darkness
hidness
underwrapped
spill the beans
semisecrecy
make known
on the hush
secret
secretive
cryptadia
in petto
hypersecrecy
hiding
supersecret
concealing
under one's hat
confidentiality
ectocrine
hypersecretion
secretional
secretionary
confidence
let the cat out of the bag
secrecy
latently
tip one's hand
hugger-mugger
semisecret
masked
covert
hypersecretory
nonsecret
submerged
secret of Polichinelle
secretly
out
buried
something nasty in the woodshed
closet
incretion
divulgation
under the table
secretable
shoot off at the mouth
unrevealed
nonsecretable
private
prosecretory
occult
backroom
hush-hush
sub rosa
in secret
hush up
on the QT
cloakedly
entrust
on the Q.T.
underhanded
oversecrete
lithia emerald
blab
peach
sing
babble out
babble
blab out
talk